D.C. voltage converter including a pulse width controlled semiconductor switch

Abstract

A d.c. voltage converter having alternating energy intake and energy discharge phases. The converter includes a power transformer having a core and at least primary, secondary and tertiary windings associated with the core. A primary circuit including a pulse width controlled semiconductor switch connected in series with the primary winding conducts an energy intake current during the energy intake phase of the converter. A secondary circuit including a smoothing capacitor and at least one rectifier element connecting the smoothing capacitor to the secondary winding conducts an energy discharge current during the energy discharge phase on the converter. Circuit means are provided for connecting the tertiary winding to the smoothing capacitor so that, following the energy discharge phase of the converter, excess energy of the smoothing capacitor in the form of an energy feedback current is fed back into the core until the start of the next energy intake phase of the converter.

What is claimed is: 
     
       1. A d.c. voltage blocking converter having energy storage phases alternating with energy discharge phases, said converter comprising: a power transformer having a core and at least primary, secondary and tertiary windings associated with said core;   a primary circuit including said primary winding and a pulse width controlled semiconductor switch connected in series with said primary winding for conducting an energy storage current during the energy storage phase of said converter;   a secondary circuit including said secondary winding, a smoothing capacitor and at least one rectifier element connecting said smoothing capacitor to said secondary winding for conducting an energy discharge current during the energy discharge phase of said converter; and   circuit means comprising a second semiconductor switch controlled by a reference signal for connecting said tertiary winding to said smoothing capacitor so that, following the energy discharge phase of said converter, excess energy of said smoothing capacitor in the form of an energy feedback current is fed back into said core until the start of the next energy storage phase of said converter.   
     
     
       2. A d.c. voltage converter having energy storage phases alternating with energy discharge phases, said converter comprising: a power transformer having a core and at least primary, secondary and tertiary windings associated with said core;   a primary circuit including said primary winding and a pulse width controlled semiconductor switch connected in series with said primary winding for conducting an energy storage current during the energy storage phase of said converter;   a secondary circuit including said secondary winding, a smoothing capacitor and at least one rectifier element connecting said smoothing capacitor to said secondary winding for conducting an energy discharge current during the energy discharge phase of said converter, said tertiary winding having a first winding end and a second winding end, said one rectifier element and said smoothing capacitor having a common connection point connected to the first winding end of said tertiary winding, and said smoothing capacitor having a remote electrode facing away from said one rectifier element;   a voltage output terminal, said converter producing an output voltage at said output voltage terminal; and   circuit means for connecting said tertiary winding to said smoothing capacitor so that, following the energy discharge phase of said converter, excess energy of said smoothing capacitor in the form of an energy feedback current is fed back into said core until the start of the next energy storage phase of said converter, said circuit means including:   a second rectifier element connected to the second winding end of said tertiary winding and oriented in the current flow direction of the feedback current which flows from said smoothing capacitor through said tertiary winding via said common connection point and back to the remote electrode of said smoothing capacitor via said second rectifier element;   a further semiconductor switch having a control electrode and forming a current switching path between said second rectifier element and the remote electrode of said smoothing capacitor;   a clock pulse synchronized sawtooth generator having an output and producing a clock pulse synchronized sawtooth signal at such output; and   a comparison device having a first input connected to the output of said sawtooth generator, a second input connected to said output voltage terminal, and an output connected to the control electrode of said further semiconductor switch, said comparison device being constructed for emitting a turn-on signal at its output for turning-on said further semiconductor switch when a monentary value of the signal at the output of said sawtooth generator falls below a monentary value of the output voltage of said converter.   
     
     
       3. A d.c. voltage converter having energy storage phases alternating with energy discharge phases, said converter comprising: a power transformer having a core and at least primary, secondary and tertiary windings associated with said core;   a primary circuit including said primary winding and a pulse width controlled semiconductor switch connected in series with said primary winding for conducting an energy storage curent during the energy storage phase of said converter;   a secondary circuit including said secondary winding, a smoothing capacitor and at least one rectifier element connecting said smoothing capacitor to said secondary winding for conducting an energy discharge current at the conclusion of the energy storage phase and during the energy discharge phase of said converter, said tertiary winding having a first winding end and a second winding end, said one rectifier element and said smoothing capacitor having a common connection point connected to the first winding end of said tertiary winding, and said smoothing capacitor having a remote electrode facing away from said one rectifier element;   an output voltage terminal, said converter producing an output voltage at said output voltage terminal;   circuit means for connecting said tertiary winding to said smoothing capacitor so that, following the energy discharge phase of said converter, excess energy of said smoothing capacitor in the form of an energy feedback current is fed back into said core until the start of the next energy storage phase of said converter, said circuit means including:   a second rectifier element connected to the second winding end of said tertiary winding and oriented in the current flow direction of feedback current flowing from said smoothing capacitor through said tertiary winding via said common connection point and back to the remote electrode of said smoothing capacitor via said second rectifier element;   a further semiconductor switch having a control electrode and forming a current switching path between said second rectifier element and the remote electrode of said smoothing capacitor;   a current measuring means having an output and connected for deriving a voltage from the energy discharge current; and   a comparison device having a first input connected to the output of said current measuring means, a second input connected to said output voltage terminal, and an output connected to the control electrode of said further semiconductor switch, said comparison device being constructed for emitting a turn-on signal for turning on said further semiconductor switch when the voltage derived from the energy discharge current by said current measuring means falls below a momentary value of the output voltage of said converter.   
     
     
       4. A converter as defined in claim 1, in combination with coupled, nonregulated secondary output circuits, wherein said power transformer includes additional windings each of which is associated with a respective one of said coupled, nonregulated secondary circuits.